Synergistic herbicidal methods and compositions comprising dinitroaniline and imidazolinone compounds

ABSTRACT

The present invention provides a method for the synergistic control of undesirable plants such as Poa, Polygonum and Setaria which comprises applying to the plants or their locus a synergistically effective amount of a combination of a dinitroaniline compound and an imidazolinone compound. Further provided are synergistic herbicidal compositions comprising dinitroaniline and imidazolinone compounds.

BACKGROUND OF THE INVENTION

Certain weeds such as Poa, Polygonum and Setaria are particularlydifficult to control. Their full-season competition can reduce cropyields and cause significant economic loss in crop production.Accordingly, a need exists in the art for an improved method for thecontrol of these undesirable plants.

SUMMARY OF THE INVENTION

Surprisingly, it has now been found that the combination of adinitroaniline compound with an imidazolinone compound providessynergistic weed control. In particular, the synergistic herbicidalmethods and compositions of this invention provide improved control ofpestiferous weeds such as Poa, Polygonum and Setaria.

The present invention provides a method for the synergistic control ofundesirable plants such as Poa, Polygonum and Setaria which comprisesapplying to the locus of said plants, to the foliage or stems of saidplants, or to the soil or water containing seeds of said plants asynergistically effective amount of a combination of a dinitroanilinecompound selected from the group consisting of pendimethalin,trifluralin, benfluralin, butralin, dinitramine, ethalfluralin,fluazinam, fluchloralin, flumetralin, oryzalin and prodiamine; and atleast one imidazolinone compound selected from the group consisting ofimazamox, the R isomer thereof or a salt thereof; imazethapyr, the Risomer thereof or a salt thereof; imazaquin, the R isomer thereof or asalt thereof; imazapic, the R isomer thereof or a salt thereof; andimazapyr, the R isomer thereof or a salt thereof; and mixtures thereof.

The present invention also provides a synergistic herbicidal compositionwhich comprises an agriculturally acceptable carrier and asynergistically effective amount of a combination of a dinitroanilinecompound selected from the group consisting of pendimethalin,trifluralin, benfluralin, butralin, dinitramine, ethalfluralin,fluazinam, fluchloralin, flumetralin, oryzalin and prodiamine; and atleast one imidazolinone compound selected from the group consisting ofimazamox, the R isomer thereof or a salt thereof; imazethapyr, the Risomer thereof or a salt thereof; imazaquin, the R isomer thereof or asalt thereof; imazapic, the R isomer thereof or a salt thereof;imazapyr, the R isomer thereof or a salt thereof; and mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, it has now been found that the application of acombination of a dinitroaniline compound plus at least one imidazolinonecompound provides synergistic control of troublesome weeds, particularlyPoa, Polygonum and Setaria. That is, the application of the combinationof the invention gives a mutual reinforcing action such that theapplication rates of the individual herbicidal components can be reducedand still the same herbicidal effect is achieved or, alternatively, theapplication of the combination of herbicidal components demonstrates agreater herbicidal effect than expected from the effect of theapplication of the individual herbicidal components when applied singlyat the rate at which they are present in the combination (synergisticeffect).

As used in the specification and claims, the terms used for theimidazolinone compounds imazamox, imazethapyr, imazaquin, imazapic andimazapyr designate the compound, the R isomer thereof, or theagriculturally acceptable salt thereof. The imidazolinone compounds andtheir corresponding chemical names are listed herein below.

Imazamox designates2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)nicotinicacid, the R isomer thereof, a salt thereof, or mixtures thereof.

Imazethapyr designates5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid,the R isomer thereof, a salt thereof, or mixtures thereof.

Imazaquin designates2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)quinolinecarboxylicacid, the R isomer thereof, a salt thereof, or mixtures thereof.

Imazapic designates2-(4-isopropyl-5-methyl-5-oxo-2-imidazolin-2-yl)-5-methylnicotinic acid,the R isomer thereof, a salt thereof, or mixtures thereof.

Imazapyr designates2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid, the Risomer thereof, a salt thereof, or mixtures thereof.

In the context of the present invention, the term agriculturallyacceptable salt includes alkali metal, ammonium, alkyl sulphonium oralkylphosphonium salt or the quatenary salt of an amine having amolecular weight of less than 300. In particular, the term includesisopropylammonium, ammonium, sodium and trimesium, especiallyisopropylammonium and ammonium.

As used in the specification and claims, the term R isomer designatesthe optical isomer of an imidazolinone compound having the Rconfiguration assigned to the assymetric carbon in the imidazolinonering which is substituted by a methyl and an isopropyl group, forexample the R isomer of the imidazolinone compound imazapyr is shownbelow.

In accordance with the method of the invention, a synergisticallyeffective amount of a combination of a dinitroaniline compound,preferably pendimethalin, and at least one imidazolinone compound,preferably imazamox, is applied to the locus of the undesirable plants,the foliage or stems of the undesirable plants or the soil or watercontaining seeds of the undesirable plants, particularly plants selectedfrom the genera Poa, Polygonum and Setaria, preferably Poa annua,Polygonum persicara and Setaria verticilliata. Advantageously,synergistic control of undesirable plant species is achieved from eitherpreemergence or postemergence application of the dinitroaniline andimidazolinone compounds.

Preferred combinations of the invention are those combinations whereinthe weight/weight (wt/wt) ratio of dinitroaniline compound:imidazolinonecompound is about 10:3 to 900:1. More preferred combinations of theinvention are combinations of pendimethalin is and an imidazolinonecompound wherein the wt/wt ratio of pendimethalin:imidazolinone compoundis about 10:3 to 900:1. Most preferred combinations of this inventionare combinations of pendimethalin and imazamox wherein the wt/wt ratioof pendimethalin:imazamox is about 20:3 to 100:1.

The synergistically effective amount of the combination of adinitroaniline compound and an imidazolinone compound may vary accordingto prevailing conditions such as the particular dinitroaniline andimidazolinone compounds present, weed pressure, application timing,weather conditions, soil conditions, mode of application, topographicalcharacter, target crop species, and the like. In general, a synergisticeffect may be achieved at application rates of about 500 g/ha to 4,500g/ha of a dinitroaniline compound in combination with about 5 g/ha to150 g/ha of an imidazolinone compound, preferably about 500 g/ha to4,500 g/ha of pendimethalin in combination with about 15 g/ha to 100g/ha of imazamox.

The present invention also provides a synergistic herbicidal compositioncomprising an agriculturally acceptable carrier and a synergisticallyeffective amount of a combination of a dinitroaniline compound and atleast one imidazolinone compound. The agriculturally acceptable carriermay be a solid or a liquid. While not required, the combinationcomposition of the invention may also contain other additives such asfertilizers, inert formulation aids, e.g. surfactants, emulsifiers,defoamers, dyes, extenders and the like.

Compositions according to the invention may be formulated in anyconventional form, for example in the form of a twin pack, or as anemulsifiable concentrate, soluble granular, dispersible granular and thelike with emulsifiable concentrates being preferred.

Preferred compositions of the invention are those compositions whereinthe dinitroaniline and imidazolinone compounds are present in a wt/wtratio of about 10:3 to 900:1 dinitroaniline compound:imidazolinonecompound. More preferred inventive compositions are those compositionswherein the dinitroaniline compound is pendimethalin and theimidazolinone compound is imazamox and the wt/wt ratio is about 20:3 to100:1 pendimethalin:imazamox.

In actual practice, a tank mix of a commercially convenient associationor presentation of a dinitroaniline compound and an imidazolinonecompound may be applied to the locus of the undesirable plants, to thefoliage or stems of the undesirable plants or to the soil or watercontaining seeds of the undesirable plants, or the dinitroanilinecompound and imidazolinone compound may be applied separately orsequentially, or the combination compositions of the invention may beapplied in a single combined form as described hereinabove.

The synergistically effective amount of a combination of adinitroaniline compound and an imidazolinone compound suitable for usein the composition of the invention is that amount sufficient to provideabout 500 g/ha to 4,500 g/ha of a dinitroaniline compound and about 5g/ha to 150 g/ha of an imidazolinone compound, preferably about 500 g/hato 4,500 g/ha of pendimethalin and about 15 g/ha to 100 g/ha ofimazamox, more preferably about 500 g/ha to 1,500 g/ha of pendimethalinand about 15 g/ha to 75 g/ha of imazamox.

The synergistic herbicidal compositions of the invention provideeffective resistance management programs in crop production, for examplepeas, soybeans or other legumes or imdazolinone/resistant/tolerant cropssuch as corn, canola, sugarbeet, wheat, rice, soybean and the like cropproduction, preferably legumes (especially peas) orimidazolinone-resistant/tolerant corn crop production.

For a more clear understanding of the invention, specific examplesthereof are set forth below. These examples are merely illustrative, andare not to be understood as limiting the scope and underlying principlesof the invention in any way.

In the following examples, synergism is determined by the Colby¹ method,i.e. the expected (or predicted) response of the combination iscalculated by taking the product of the observed response for eachindividual component of the combination when applied alone divided by100 and subtracting this value from the sum of the observed response foreach component when applied alone. Synergism of the combination is thendetermined by comparing the observed response of the combination to theexpected (or predicted) response as calculated from the observedresponses of each individual component alone.

The foregoing is illustrated mathematically below, wherein acombination, C, is composed of component A plus component B and Obs.designates the observed response of the combination C. $\begin{matrix}{{\left( {A + B} \right) - \frac{AB}{100}} = \quad {{Expected}\quad {response}\quad \left( {{Exp}.} \right)}} \\{{Synergism} \equiv \quad \left( {{Obs}.{- {{Exp}.}}} \right) > 0}\end{matrix}$

¹Colby, S. R., Weeds, 1967(15), p. 20-22

EXAMPLE 1 Evaluation of the Herbicidal Activity of a Combination ofPendimethalin and Imazamox

Formulations containing imazamox¹, pendimethalin² and animazamox/pendimethalin combination³ are diluted with water and appliedpreemergence at volumes of 200 L/ha to 400 L/ha to field plots toprovide the rates shown in Table 1. 60 days after application, the plotsare visually evaluted for percent weed control. The results aresummarized in Table 1. If more than one plot is included in anevaluation, the results are averaged.

¹BOLERO®40 SL, an imazamox aqueous concentrate commercially availablefrom American Cyanamid Company, Parsippany, N.J.

²STOMP®400 SC, a pendimethalin suspension concentrate commerciallyavailable from American Cyanamid Company, Parsippany, N.J.

³An emulsifiable concentrate containing imazamox and pendimethalin.

As can be seen from the data in Table 1, application of a combination ofpendimethalin plus imazamox gives greater control of Poa annua,Polygonum persicara and Setaria verticilliata than that which could bepredicted from the weed control resulting from the application of eitherpendimethalin or imazamox alone.

TABLE I Evaluation of Weed Control % Weed Control Imazamox PendimethalinEx- (Obs. Weed Species g/ha g/ha Observed pected Exp.) Poa annua 0 1,12563 — 75 0 68 — 75 1,125 97 88 9 Polygonum 0 1,125 76 — persicaria 75 066 — 75 1,125 100 92 8 Setaria 0 1,125 86 — verticilliata 75 0 45 — 751,125 96 92 4

What is claimed is:
 1. A herbicidal composition for the synergisticcontrol of undesirable Poa, Polygonum or Setaria plants whichcomposition comprises an agriculturally acceptable carrier and asynergistically effective amount of a combination of pendimethalin andimazamox.
 2. A method for the synergistic control of undesirable Poa,Polygonum or Setaria plants which comprises applying to the locus ofsaid plants, to the foliage or stems of said plants or to the soil orwater containing seeds of said plants a synergistically effective amountof a combination of pendimethalin and imazamox.
 3. The method accordingto claim 2 wherein said plants are Poa annua, Polygonum persicaria orSetaria verticilliata.
 4. The method according to claim 2 wherein saidplants are Poa annua or Polygonum persicaria.
 5. The method according toclaim 2 wherein the pendimethalin and imazamox are present at a wt/wtratio of about 20:3 to 100:1.
 6. The method according to claim 5,wherein said plants are Poa annua or Polygonum persicaria.
 7. The methodaccording to claim 6, wherein the synergistically effective amount isabout 500 g/ha to 4,500 g/ha of pendimethalin and about 15 g/ha to 100g/ha of imazamox.
 8. The method according to claim 2 wherein thependimethalin and imazamox are present at a wt/wt ratio of about 10:3 to900:1.
 9. The method according to claim 2 wherein the synergisticallyeffective amount is about 500 g/ha to 4,500 g/ha of pendimethalin andabout 5 g/ha to 150 g/ha of imazamox.